Submarine volcano

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Lō‘ihi SeamountComputer-generated image of the summit area of Lō‘ihi, a submarine volcano southeast of the island of Hawaii. Lō‘ihi shares the same “hot spot” on Earth's crust that has formed Mauna Loa and Kilauea volcanoes on Hawaii.Image courtesy of John R. Smith, Hawai'i Undersea Research Lab at SOEST, University of Hawai'i/ Encyclopædia Britannica, Inc.

Volcanic activity and the Earth's tectonic plates

Stratovolcanoes tend to form at subduction zones, or convergent plate margins, where an oceanic plate slides beneath a continental plate and contributes to the rise of magma to the surface. At rift zones, or divergent margins, shield volcanoes tend to form as two oceanic plates pull slowly apart and magma effuses upward through the gap. Volcanoes are not generally found at strike-slip zones, where two plates slide laterally past each other. “Hot spot” volcanoes may form where plumes of lava rise from deep within the mantle to the Earth's crust far from any plate margins.

Encyclopædia Britannica, Inc.

Learn about this topic in these articles:

major reference

…its two persistent rift zones.
These structures occur in various forms, but many are cone-shaped seamounts. Some ancient island volcanoes were eroded flat or covered with a coral cap at sea level before they sank below the sea surface as they and the crust supporting them cooled and…

banded-iron formations

…containing a significant proportion of submarine volcanic rocks, and for this reason it is generally accepted that such deposits formed as a result of submarine volcanism. Such a conclusion is supported by two simple observations: first, that many volcanogenic massive sulfide deposits, such as those in New Brunswick, Canada, are…

ocean salinity

…carrying dissolved salts from the magmatic material within the crust. It may lose much of its dissolved load to precipitates on the seafloor and gradually blend in with the surrounding seawater, sharing its remaining dissolved substances.